MIAMI -- Landon Donovan will not play for the U.S. national team in a pair of upcoming World Cup qualifying matches because of an injured left knee, adding to what will be a pressure-filled few days for the Americans.

U.S. Soccer said Tuesday that Donovan -- who has more goals, assists and starts than any player in program history -- likely will not be replaced on what was a 24-man roster for the upcoming qualifiers, first on Friday on the road against Antigua and Barbuda, then in Kansas City on Oct. 16 against Guatemala.

Donovan was injured while playing Saturday for the Los Angeles Galaxy. He was selected by U.S. coach Jurgen Klinsmann for these qualifiers anyway, and the team's athletic trainers wanted him to be evaluated one more time before he started training.

Donovan had scrapped plans for an MRI in Los Angeles on Monday because he thought his knee had improved.

"Landon was very optimistic over the weekend when his knee was feeling much better, but now he needs time to recover," Klinsmann said.

Both the national team and the Galaxy said Donovan was returning to Los Angeles for further evaluation.

That was not the outcome anyone expected. Hours before the Donovan decision was announced, Klinsmann said the Americans had "very, very positive" news about his status.

"You want your leaders on the team there," Klinsmann said.

Brek Shea also was was ruled out of the qualifiers on Tuesday because of an abdominal injury. Barring a change of plans, that means Klinsmann will take only 22 players to Antigua for what would seem to be a must-win match on Friday night.

"We knew Brek was a question mark coming in, and now we have a clear picture of where he stands," Klinsmann said. "We feel confident that the group we have will get the job done."

It is not shaping up as an easy task, with three teams playing for two spots in next year's regional finals.

The U.S., Guatemala and Jamaica all have seven points after the first four matches of play in this qualifying round, while Antigua and Barbuda has one point. For the U.S. to reach next year's regional finals, four points -- a win and a tie -- would seem to be the most probable requirement.

Guatemala figures to have the toughest draw remaining of the three teams atop Group A, having to play both Jamaica (which would be the odd team out because of a goal-differential tiebreaker) and the U.S.

If the Americans win on Friday, they would control their destiny as far as reaching the next round, no matter what the Guatemala-Jamaica result is that same night.

"You don't want to rely on other people," U.S. goalkeeper Tim Howard said. "We should have done business before these two games, but we didn't, so now there's pressure on us to do that."

There was some good news on the injury front for the Americans on Tuesday, with midfielder Michael Bradley able to train with teammates. Bradley has been dealing with a leg injury.

About 10 of the 24 players on the roster missed a Tuesday morning training session for a variety of reasons -- from jet lag to treatment of minor injuries. Klinsmann said he expected the full roster to be available for a gym session later in the day, and the assumption was that they would all be ready for training Wednesday as well.

Midfielder Jermaine Jones (left ankle) was among those not at training on Tuesday; he leads all American players in appearances (10) and minutes (877) this year, and the expectation is he will be able to play on Friday. And with the way the injuries are shaking out, Graham Zusi would most likely get the call to play on the wide right side of the midfield.

"We're here to get six points," Klinsmann said. "This is our goal and what we want to achieve."